Stress-relieving device for electrical plugs



June 4, 1968 D. G. WHEELER 3,387,254

STRESS-RELIEVING DEVICE FOR ELECTRICAL PLUGS Filed Nov. 7, 1966 INVENTOR. DAV/D 6. WHEELER \ow'nsend n [aumsend A TTORNEYS.

United States Patent Oflice 3,387,254 Patented June 4, 1968 3,387,254 STRESS-RELIEVING DEVICE FOR ELECTRICAL PLUGS David G. Wheeler, 1763 Orleans Court, Walnut Creek, Calif. 94598 Filed Nov. 7, 1966, Ser. No. 592,531 Claims. (Cl. 339-103) This invention relates to electrical plug connectors.

Electrical cords are conventionally attached to their plug connectors in such a manner that when the male and female plugs are relatively removed from each other, there is a psychological tendency of the operator to pull the cord rather than the plug structure itself. In such instances, the electrical conductors interior of the cord are frequently severed from contact with the connector thereby causing shorts and open circuits.

Previously, certain plug constructions have been formed which provide a sufficient grip on the plug so that the aforesaid problem is greatly minimized. However, there are still many connectors in which the weak link in the physical construction of the plug arrangement is the connection of the conductor interior of the cord to the plug assembly itself.

The subject invention is concerned with an apparatus which can be mounted on conventional electrical plugs in such a way as to mechanically grip the cord at a position spaced from the connector and transmit the plug removing force through the device to the body or housing of the plug, thus avoiding stressing of the cord conductor.

A feature and advantage of the device lies in the fact that pulling the cord leading to the plug stresses the cord at the connection to the adapter of thisinvention whereby the pulling force is then transmitted to the plug housing itself. There is provided a slack excess of the electrical cord between the point of contact with the adapter and with the plug housing which completely isolates the juncture of the electrical conductor from pulling stress at the housing.

A further object of this invention lies in the fact that it can be readily attached to existing connectors without in any way modifying the electrical conductor connection to the plug.

A further objective of this invention is to frictionally reinforce the attachment of a plug to its adjoined cord by providing a compressive cord gripping. clamp which utilizes an interposing layer of dielectric material so as to uniformly grip the cord over a portion of its length and provide the insulation necessary for safe friction plug attachment.

Other objects, features and advantages of the present invention will be more apparent after referring to the following specification and drawings in which:

FIG. 1 is a plan view of a male plug connector with a stress relief attachment installed thereon;

FIG. 2 is a side view of a female plug connector with a stress relief attachment installed thereto;

FIG. 3 is an end view of a plug connector and stress relief attachment according to the present invention;

FIG. 4 is a plan view of that portion of the attachment which is installed to the cord of the plug connector; and

FIG. 5 is a plan view of a plug connector with an installed alternate embodiment of the stress relief attachment.

With reference to the drawings and in particular to FIGS. 1, 2 and 3 thereof, stress relief attachment 15 is shown attached to connector housing 17 and its appended cord 18. As can be seen in the partial section of FIG. 1, cord 18 is attached to housing 17 through its internal conductor 20 at conductive member 22. Without the attachment of stress relief attachment 15, any tensional or pulling force on cord 18 will be transferred to housing 17 through conductor 20. As conductor 20 is chosen for its electrical properties and not for its tensile strength, this element represents the weakest link in the connectorcord union and tensional failures frequently occur along its length. While this defect is frequently remedied in the art by the attachment of an entirely different housing which securely grips the cord independent of conductor 20, such a correction wastes the plug connector originally furnished with the appliance, requires the furnishing of a substitute housing, and makes the relatively laborious alteration of the internal electrical communications of the connector necessary. Accordingly, the present invention relates to a simple stress relief attachment which reinforces such a connector-cord union utilizing the original housing 17.

Stress relief attachment 15 is composed essentially of two main components: flexible dielectric belt or loop 25 and compressible clamp 30. Belt or loop 25 is typically a flat, endless strip of flexible dielectric material such as plastic, nylon and the like. Typically, loop 25 is curved normal to its fiat surface and has a circumference which is larger in diameter than housing 17. In width, loop 25 is slightly wider than that portion of housing 17 which it is designed to adjoin but has a small thickness normal to its fiat surface which will not appreciably interfere with the penetration of the associated conductive member 22 when the connector is installed for electrical communication with a mating connector. Clamp 39 is comprised typically of a strip of soft metal, such as copper and the like, which may be pre-formed to fit over both cord 18 and a wrapped portion of loop 25, as will hereinafter become apparent. In width, clamp 30 is equal to or less than the width of loop 25 so that the material of the clamp will not be in direct contact with the insulation of cord 18.

In the installation of stress relief attachment 15, loop 25 is adjoined along its interior flat surface to housing 17 at first portion or end 33. End 33 is configured with apertures 36 therein which are medially located on the width of loop 25 and are of sufficient size to allow passage of conductive member 22. If housing 17 is a male member (as illustrated in FIG. 1), apertures 36 are fitted over conductive members 22, thereby centering loop 25 in its mating engagement with the housing. Alternatively, if housing 17' is a female member (as illustrated in FIG. 2), first portion 33 is centered in its making engagement with housing 17' so that members 22 of a male connector may pass through apertures 36. As is readily apparent, both mating engagements may be adhesively reinforced with glue and the like to secure loop 25 to housing 17.

Second portion 35 is wrapped about cord 18 so as to slack the cord between the point where it is wrapped and housing 17. Clamp 3th is attached to loop 25 at second portion 35 receiving cord 18 in locked engagement with the dielectric of loop 25 therebetween. Typically, clamp 30 is attached by pliers 40 as illustrated in FIG. 4. In the compressed position, clamp 30 typically encompasses more than of the periphery or circumference of cord 18. This mode of frictional attachment utilizes the interposed dielectric material to uniformly grip cord 18 over a section of its length distributing the compressive load of the locked engagement and at the same time reinforcing the electrical insulation at the point of attachment.

When an operator extracts the connector by pulling on cord 18 from beyond attachment 15, loop 25 is tensionally stressed due to its frictional attachment to the cord. Loop 25 compresses at first portion 33 against housing 17, in effect pushing the housing out of engagement with the mating connector. Conductor 20 is not stressed as cord 18 is slack between its locked engagement with clamp 30 and housing 17.

An alternate embodiment of attachment is shown in FIG. 5, utilizing dielectric band 44 in place of loop 25. Band 44 is identical in dimension to loop 25 with the exception that its ends are not joined to form an endless belt. The band 44, longerin length than housing 17, is attached to the housing in a manner similar to the attachment of loop 25' as hereinbefore described. The ends of band 44, illustrated in FIG. 5, are embracingly wrapped about cord 18 at a distance from housing 17 so that the cord is slack between the place where it is wrapped and the housing. Clamp 30 is attached to the ends of band 44 and receives cord 18 in locked engagement when compressively attached.

As is apparent, the present invention may be readily adapted to connector housings which have any number of conductive members associated therewith. Further, the apertures may be varied in size to include more than one conductive member. While two embodiments of the present invention have been shown and described, it will be apparent that other adaptations and modifications can be made without departing from the spirit and scope of the disclosed invention as limitedby the appended claims.

What is claimed is:

1. A stress-relieving device for electrical plug connectors of the type having a housing with at least one conductive member associated therewith and a cord connected to said housing by a conductor interior of said cord, said device comprising: an endless flexible dielectric loop having a size greater than said housing; said loop having first and second portions on diametrically opposite ends thereof; means on said first portion to connect the face of said housing to said loop with said housing being located on the interior of said loop; clamp means mounted to the second portion of said loop to receive said cord in locked engagement therewith, said cord being looped between said clamp means and said housing sufificiently to relieve tensional forces applied to said cord at the juncture of the electrical connector and said cord.

2. A stress-relieving device for electrical plug connectors according to claim 1 wherein: said conductor member is formed of a protruding element and said means on said first portion comprises a medial aperture configured for receiving said protruding element whereby said loop is centered on said face by said member in the position of attachment.

3. A stress-relieving device for electrical plug connectors according to claim 1 wherein: said clamp means comprises a metallic clamp externally mounted about said cord with said loop 'therebetween.

4. A stress-relieving device for electrical plug connectors according to claim 3 wherein: said means of said metallic clamp encompasses more than 180 degrees of the periphery of said cord.

5. A stresselieving device for electrical plug connectors of the type having a housing with at least one conductive member associated therewith and a cord connected to said housing by a conductor interior of said cord, said device comprising: a flexible dielectric band having a length greater than the length of said housing; means on said band for attachment of said band to said housing; clamp means mounted to portion of said band to receive said cord in clamped engagement therewith, said clamped engagement including at least one of said portions of said band wrapped in embracing relation about said cord, said cord being slack between said clamp means and said housing sufficiently to relieve tensional forces applied to said cord at the juncture of the electrical connector and said cord.

References Cited UNITED STATES PATENTS 1,262,155 4/1918 Zimmerman 339-276 X 1,765,035 6/1930 Stubbs.

2,136,850 11/1938 Honey 339-103 2,761,109 8/1956 Hacker 33975 3,187,293 6/1965 Jacobus 339l03 3,215,971 11/1965 Caparosa 339 RICHARD E. MOORE, Primary Examiner. 

1. A STRESS-RELIEVING DEVICE FOR ELECTRICAL PLUG CONNECTORS OF THE TYPE HAVING A HOUSING WITH AT LEAST ONE CONDUCTIVE MEMBER ASSOCIATED THEREWITH AND A CORD CONNECTED TO SAID HOUSING BY A CONDUCTOR INTERIOR OF SAID CORD, SAID DEVICE COMPRISING: AN ENDLESS FLEXIBLE DIELECTRIC LOOP HAVING A SIZE GREATER THAN SAID HOUSING; SAID LOOP HAVING FIRST AND SECOND PORTIONS ON DIAMETRICALLY OPPOSITE ENDS THEREOF; MEANS ON SAID FIRST PORTION TO CONNECT THE FACE OF SAID HOUSING TO SAID LOOP WITH SAID HOUSING BEING LOCATED ON THE INTERIOR OF SAID LOOP; CLAMP MEANS MOUNTED TO THE SECOND PORTION OF SAID LOOP TO RECEIVE SAID CORD IN LOCKED ENGAGEMENT THEREWITH, SAID CORD BEING LOOPED BETWEEN SAID CLAMP MEANS AND SAID HOUSING SUFFICIENTLY TO RELIEVE TENSIONAL FORCES APPLIED TO SAID CORD AT THE JUNCTURE OF THE ELECTRICAL CONNECTOR AND SAID CORD. 